1. Field of the Invention
In general, the invention relates to conductive ball joints, and to lamps and other structures using the conductive ball joints.
2. Description of Related Art
Ball joints are used to join two structures while allowing one to move with respect to another in multiple planes. A typical ball joint comprises a spherical or hemispherical “ball” mounted on the end of a first structure and a complementary socket on a second structure. The ball is received in and permitted to move within the socket, allowing the two structures to move relative to one another with up to three degrees of freedom.
Ball joints are common in many different types of machines, ranging from automobiles to lighting fixtures, and have been implemented in many different sizes, with different materials, and with different load-carrying capacities. In some cases, a ball joint simply provides mechanical connection and load transmission between and through the structures that it connects.
In many cases, it is necessary to transmit some form of electricity or electrical signal past or through the ball joint. Typically, this is done by creating a hole or bore through the ball of the ball joint and inserting wires through the hole or bore to carry the signal. Wires can also be routed around the joint in some cases. While common, these types of solutions can be problematic. For example, the presence of the wires can restrict the range of motion of the ball joint, and continued motion can strain or wear the insulation on the wires, raising the possibility of electrical short.
U.S. Pat. No. 7,061,169 to Fung purports to disclose a solution to this problem: an electrically conductive ball, split into two equally-sized, electrically isolated conductive halves by an insulator, to carry both voltage and ground. The socket in which the conductive ball rests is similarly electrically conductive. However, the Fung conductive ball joint is problematic, as it appears that the circuit will short out as the ball moves through its full range of motion.
Effective, reliable means for transmitting electricity and electrical signals past or through ball joints would be particularly useful for lighting fixtures and other products which are frequently repositioned, and in which a relatively large range of motion is desirable.